Method of separating wood-tars and pyroligrneous acid



W. E. CLIFFORD.

METHOD H SEPAHATING WOOD TARS AND PYROLIGNEOUS ACID.

APPLICATION FILED JUNE 25,1918.

1,889,022. e ed May 4,1920.

I I Q I- guucnfoz William EClifforcL 3 WM M/ WILLIAM E. CLIFFORD, OFMEMPHIS, TENNESSEE.

METHOD OF SEPARATING WOOD-TABS AND PYROLIGNEOUS ACID.

Specification of Letters Patent.

Patented M215 4, 1920.

Application filed June 25, 1918. Serial No. 241,784.

To all whom it may concern:

Be it known that I, lVILLLAM E. CLIFFORD, a citizen of the UnitedStates, residing at Memphis, Shelby county, and State of Tennessee, haveinvented and discovered certain new and useful Improvements in Methodsof Separating VVood-Tars and Pyroligneous Acid, of which the followingis a specification.

My present invention relates to a method of separating wood tars andpyroligneous acid by the application of heat and agitation and consistsin the combinations and arrangements of elements of the apparatus andthe steps of procedure hereinafter described and particularly set forthin the accompanying claims.

It is the accepted practice at the present time in practically all, ifnot all of the plants engaged ,in the destructive distillation of woodin this country, to collect the total distillate from the retorts, ovensand kilns, (this distillate consisting of pyroligneous acid and tar)into .one large tank, and from there it is pumped to a series or batteryof tanks, known as settling tanks, and here the combined pyroligneousacid and tar is allowed to settle for a time. The tar owing to itsgreater specific gravity settles to the bottom of the tanks, and the.greater portion of the pyroligneous acid liquor floats on the top andis run off and worked up in the usual way.

The tar which settles to the bottom of the tanks and which still retainswith it from 20% to 30% of pyroligneous acid liquor is run oil? intolarge copper stills and heat applied first by means of a steam coil andlater when no further distillate comes over, live steam is admittedwhich carries off the remaining pyroligneous acid and also portions ofthe light and heavy oils from the tar. These oils are not distilled butare carried over mechanically.

This process of distillation by means of a steam coil and live steam,although it may remove the pyroligneous acid liquor, which the wooddistiller is anxious to recover, has its disadvantages, in that itcarries over portions of the light and heavy oils from the tar whichhave to be removed from the pyroligneous acid liquor by settling beforeit can be neutralized with lime for the production of calcium acetate.The process of distillation by means of a steam coil and live steam,also breaks down the tar as above stated by mechanically carrying overportions of the light and heavy oils. The breaking down of the tarrenders it of no particular value except as fuel and-the cost of theapparatus is considerable as also is the cost of operation.

During the past three or four years there has been a growing demand forwood tar products, for use in the manufacture of creosote oils, and oilsfor the flotation of ores, and considerable work has been carried out onthe tar remaining in the stills after the distillation by steam coil andlive steam, particularly along the lines of completely distilling thetar by means of open fired stills, (that is after the first distillationby means of the steam coil and live steam the tar remaining was run intoanother type of still and here heat was applied by means of direct fireto remove the remaining oils and thus leave a residue of liquid pitch inthe still). Owing to the broken down condition of the tar from itsprevious distillation with the steam coil and live steam it was notfound at all suitable for distillation by direct fire, and there areconsiderable risks attending theattempts to distil this broken down tarby this method, and in particular its tendency to coke in the stills.

My invention which comprises a simple but elfective process obviates thedisadvantages of the prior art producing a tar containing but a smallpercentage of pyroligneous acid, which does not coke when distilled andthe py'roligneous acid produced contains less tarry matter than the acidformed by previous processes. Essentially my process comprises confiningcrude wood tar in a tank, subjecting the same to gentle heat andmoderate agitation as by an inert. gas. such as air, producing a tarsubstantially free from watery constituents. T 0 improve the quality ofthe tar agitation as by a gas is continued for a short time after theheat is cut off.

The process of de-hydration has long been practised in certainindustries, but as far as known has never been applied to the separationof the pyroligneous acid liquor and tars derived from the destructivedistillation of woods, along the lines herein stated. a

The apparatus disclosed herein has been found suitable for carrying outthe method or process of separating wood tars andpyroligneous acidliquor other than that of distillation, and the production of tars ofeven from the greater portion of pyroligneous acid liquor in the usualsettling tanks but which tar still retains from to 30% of pyroligneousacid liquor is run into the tank 3 and air is admitted to the bottom ofthe tank through the pipe 4 having a plurality of apertured branches 5and simultaneously therewith steam is passedthrough the pipe coil 6.Only sufiicient air is admitted to keep the mass in gentle motion andsimultaneously the temperature is gradually raised,

care being taken that it does not exceed 85 0. (185 F.) The total timeof heating and bringing the mass to this point is approximately one hourwhen the steam 1s shut off and the air allowed to keep this mass inmotion for about fifteen minutes after the steam is stopped. The passageof air is then discontinued and the whole allowed to come to rest andafter standing for about one hour the bulk of the pyroligneous acidliquor will be found floating on the surface of the tar and there willbe a clearly defined line of separation. The depth of the pyroligneousacid liquor on the top of the tar depends on the quantity retained bythe original tar, and theinumber of gallons of pyroligneous acid liquorand tar admitted to the tank at the commencement of the operation. Thereis no limit to the quantity which may be handled at one time since it isas easy to handle and separate 20,000 gallons as it is 2000 gallons. Theseparated tar and pyroligneous acid liquor may now be drawn off and thepyroligneous acid liquor worked up in theusual way for the production ofcalcium acetate, and the tar which now contains but from 2.}% to 4% ofpyroligneous acid liquor can be pumped to storage tanks and from thererun to the different fired stills where it may be distilled withoutdifficulty as to coking, and the remaining 2.-}% to 4% pyroligneous acidliquor will be recovered during the distillation of the tar for theproduction of valuable wood oils, creosote, guaiacol, pitch, etc.

The air which is admitted'to the bottom of the tank through theperforated pipes obtains certain results that could not be obtained byany other means, 6. 9., keeping the mass in motion and affording an evendistribution of the heat from the steam coils throughout the whole bodyof the pyroligneous acid and woodtar; to strip the adhering pyroligneousacid liquor from the wood surface of the liquor. The inventor believesthat the pyroligneous acid liquor and wood tar are not in a state ofcombination but rather in the colloid state, i. e., the pyroligneousacid liquor adheres to the surface of the tar globules. Apparently theglobules under the influence of the heat expand and present thepyroligneous acid liquor in a more susceptible condition to the actionof the air which air passing through the whole body or mass ofpyroligneous acid liquor or wood tar strips the pyroligneous acid liquorand carries it to the liquid surface. Owing to the lighter specificgravity of the pyroligneous acid liquor it will remain on the surfaceuntil it is drawn off, and this pyroligneous acid liquor once separatedby this process will not again unite with the wood tar either by coolingor by agitation. By this process the pyroligneous acid content isreduced from 2%% to 4% and the resulting tar is in a satisfactorycondition for distillation from direct fired stills.

The temperature is an important consideration in the working of thisprocess or vided with an angle thermometer 7 having its stem 8 insertedlaterally through the wall of the tank and immersed inthe pyroligneousacid liquor and tar for at least 6 inches. It is proposed to cover bythis method or process all temperature ranging from between 10 C. and 850. Care must be taken that the temperature is not allowed to exceed thispoint as by doing so there is considerable risk of losing valuableproducts. The most favorable temperatures, 2'. e., those at which themost perfect separations can be secured, lies between 50 C. (122 F.) andC. (158 F.).

The object of this process or method of separating pyroligneous and woodtars produced by and from the destructive distillation of woods, onwhich it is, desired to secure patent rights, is first the production ofa grade of wood tar which is suitable for,

.method and to this end the tank 3 is proand can be successfullydistilled from direct tillation of hardwood or woods'of the decidconiferspecies, also this process or method is one which will reduce the costof handling and separating the pyroligneous acid and wood tars in thechemical plants producing same by eliminating the use of costlvequipment, in the shape of stills and condensers, and by reducing thetime of han- 'uous species, and softwood or woods of the 120 or allplants engaged in the destructive distion of the d'ling these productsby which the separapyroligneous acid and wood tars is effected.

The method .in general use in the plants to-day engaged in thedestructive distillation of woods for the separation of the pyroligneousacid and wood tars is by distillation, this process is long and costly,a still having 'the capacity'of from 3,000 to 4,000 gallons would takeunder present methods of operation from 18 to 24.- hours to distill offthe pyroligneous acid liquor from the tar, re-

quiring considerable fuel for the production of steam, and largequantities of water for cooling the condensers, and in the end theresidual tar is not suitable for distillation in direct fired stills.

This same volume of pyroligneous acid liquorand wood tar can beseparated by the process or method herein described and the pyroligneousacid content reduced to 2%% to 4% in from 2 to 3 hours, at a small costfor steam, air and labor and the resulting tar would be in a mostsatisfactory condition for distillation from direct fired stills, forthe production of valuable oils and pitch. The latter process does notcause the tar to deteriorate by the operation.

It is intended by the use of the terms aerating and air in the claims toinclude not only the use of air but other similar gases having nocombining action on the materials in the tank, such as carbondioxid andother permanent gases.

Having thus fully described my said invention, What I claim as new anddesire to secure by Letters Patent is:

1. The method of separating wood tars and pyroligneous acid liquorswhich consists in aerating the mixture and simultaneously heating thesame to not exceeding 85 0., substantially as set forth.

2. The method of separating wood tars and pyroligneous acid liquorswhich consists in aerating the mixture and simultaneously heating thesame for about one hour to not exceeding 85 0., substantially as setforth.

3. The method of separating admixed wood tars and pyroligneous acidliquors which consists in maintaining the mixture at a temperaturebetween 10 0. and 85 0. and simultaneously agitating the same byaeration.

4. The method of separating wood tars and pyroligneous acid liquorswhich consists in aerating the mixture and simultaneously heating thesame for about one hour to not exceeding 85 0., then shutting off theheat and keeping the mass in motion by air alone until ready forcooling, substantially as set forth.

5. The method of separating wood tars and pyroligneous acid liquorswhich consists in aeratin ously heating t e same for about one hour themixture and simultaneto not exceeding 85 "0., shutting off the heat andkeeping the mass in motion by air alone for about fifteen minutes, andthen allowing it to cool, substantially as set forth.

6. The method of separating wood tars and pyroligneous acid liquorswhich consists in aerating the mixture by injecting streams of air atthe bottom thereof, and simultaneously heating the same for about onehour to not exceeding 85 0., shutting off the heat and keeping the massin motion by air alone for about fifteen minutes, then allowing. it tocool, and finally allowing to stand for about one hour and drawing offthe pyroligneous acid, substantially as set forth.

7 The method of recovering wood tars from mixtures containing the sameintimately associated with immiscible liquids.

which consists in maintaining the mixture at a temperature of not lessthan 10 0. or more than 85 0., and simultaneously agitating the same,substantially as set forth.

8. The method of recovering wood t'ars from mixtures containing the sameintimately associated with immiscible liquids which consists in aeratingthe mixture and simultaneously heating the same by steam for about onehour to not exceeding 85 0., then shutting off the steam and keeping themass in motion by air alone until ready for cooling, substantially asset forth.

9. The method of recovering wood tars from mixtures containing the sameintimately associated with immiscible liquids which consists in aeratingthe mixture byinjecting streams of air at the bottom there of, andsimultaneously heating the same for about one hour to not exceeding 850., shutting off the heat and keeping the mass in motion by air alonefor about fifteen minutes and then allowing it to cool, substantially asset forth.

and pyroligneous acid liquors, which con I sists in slowly heating themixture up to a temperature of about 859 in a period of from about oneto three hours, simultaneouslyagitating the same, cutting off the heatand continuing the agitation for a short time.

13. The method of separating wood tars and pyroligneous acid liquors,which conmy hand and seal at Memphis,- Tennessee, sists in slowlyheating the mixture up to a this 19th day of June, A. D. nineteen hun-10 temperature between 50 and 70 C. in a dred and eighteen.

period of about one hour simultaneously 5 agitating the same, cuttingofi' the heat and WILLIAM CLIFFORD- continuing the agitation for about15 Witnesses: minutes R. ELMo PULLIN,

In witness whereof, I have hereunto set JOHN W. FABLEY.

